The leak in the system is consolidated tax base, not different tax rates. That is, booking revenue (especially digital revenue) from sales across the whole of the EU in a single EU country for tax purposes promotes a race to the bottom. The right answer is to tax in proportion to the economic activity per country - https://en.wikipedia.org/wiki/Common_Consolidated_Corporate_... .
Unified corporate and income tax rates aren't a smart idea. There's no good reason to force one government to be less efficient than another.
Finally, the bailout (and to be clear: loans, not free money, and loans that were paid off early because they had higher interest rate than was available on the market) of Ireland was an indirect support for banks in other countries that had capital surplus for some years, Germany especially. The ECB forced Ireland to prevent bondholders from taking any losses - https://www.irishtimes.com/news/politics/ecb-refusal-on-bond...